Prove that similar matrices have the same rank

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SUMMARY

Similar matrices, defined by the relationship B = P-1AP, where A, B, and P are n x n matrices, have the same rank. The invertibility of matrix P ensures that rank(P) = n, which preserves the rank of matrix A when multiplied by P. Consequently, it is established that rank(B) equals rank(A). This conclusion is reinforced by the symmetric property of matrix similarity, confirming that if A is similar to B, then B is similar to A.

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Homework Statement



Prove that similar matrices have the same rank.


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The Attempt at a Solution



Similar matrices are related via: B = P-1AP, where B, A and P are nxn matrices..
since P is invertible, it rank(P) = n, and so since the main diagonal of P all > 0, multiplying by P will not change the rank of A, so rank B = rank A.

Is that seem right?
 
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If you can show that rank(P-1AP) is less than or equal to rank(A), then you are done since matrix similarity is symmetric (if A is similar to B, then B is similar to A).
 

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